This invention relates to a fluorescent lamp, and more particularly to a fluorescent lamp having auxiliary electrodes for preventing irregular light flickering and early blackening.
When a fluorescent lamp is operated by an AC power source, variation of the radiated light from the fluorescent lamp is sometimes observed. The variation of the radiated light, or flickering, is classified into two types of flickering; one is a regular flickering occurring in accordance with the frequency of the AC power source of the lamp, and the other is irregular flickering in which luminance irregularly varies independent of the frequency. The irregular flickering is annoying to the user. The irregular flickering is known to occur when the anode vibration irregularly repeats in the fluorescent lamp. Especially when the lamp has been operated 1,000 hours or over, the irregular flickering occurs more frequently.
In general, a fluorescent lamp has a pair of discharge electrodes, each of which includes a pair of leads, and an electrode filament made of tungsten coil bridging the paired leads. For preventing the irregular flickering, there is known a measure using auxiliary electrodes protruding from the leads. The measure can successfully solve the problem of irregular flickering. However, this effect of the flickering prevention does not last till the life of the fluorescent lamp expires. The possibility of reoccurrence of the annoying irregular flickering still remains. Some of the fluorescent lamps thus constructed are blackened near the electrodes comparatively early in life, resulting in shorter life.